Draper headers generally include a header frame, an elongate cutter bar along a front edge of the frame including a cutter bar beam which carries a plurality of knife guards for guiding reciprocating movement of a sickle knife across a front edge of the cutter bar. On the header is also mounted a draper assembly including a first and second draper guide roller each arranged at a respective end of the draper assembly spaced apart along the cutter bar with an axis of each roller extending substantially at right angles to the cutter bar, a draper canvas forming a continuous loop of flexible material wrapped around the rollers so as to define a front edge of the canvas adjacent the cutter bar, a rear edge of the canvas spaced rearwardly of the cutter bar, an upper run of the canvas on top of the roller and a lower run of the canvas below the rollers. The cut crop thus falls rearwardly onto the upper run of the canvas and is transported longitudinally of the header. It is necessary in between the draper rollers to provide a support plate assembly for the upper run of the draper canvas to prevent sagging. This support plate assembly includes a front support plate arranged underneath the front edge of the upper run of the draper canvas and projecting forwardly therefrom for engagement with and support by the cutter bar.
The header of this type can be used simply for forming a swath in which case the material is carried to a discharge opening of the header and deposited therefrom onto the ground. Headers of this type can also be used for feeding a combine harvester so that the materials are carried to an adapter member positioned at the discharge opening of the header for carrying the materials from the discharge opening into the feeder housing of the combine harvester. Yet further, headers of this type can be used for hay conditioners in which the material from the discharge opening is carried into crushing rolls. It will be appreciated, therefore, that the use of the header is not limited to particular types of agricultural machine but can be used with any such machine in which it is necessary to cut a standing crop and to transport that crop when cut longitudinally of the header for operation thereon.
The draper canvas normally comprises a fabric which is coated with a rubber material which is then vulcanized after forming of the fabric into the required shape and after attachment thereto of transverse slats.
One problem which arises with this combination of cutter bar and draper is that of the penetration between the draper and the cutter bar of materials including hay juices, mud and other particles carried by the cut crop. Such materials in the absence of any sealing effect enter the space between the drapers and form a very hard substance that sticks to the draper support plate and the rollers and can interfere with the proper operation of these elements, in some cases leading to damage.
Attempts have therefore been made to provide a seal between the front edge of the upper run of the draper canvas and the rear edge of the cutter bar. Up till now, however, these attempts have not achieved a complete solution to the problem.
One previous proposal made by John Deere approximately 25 years ago and is shown in the Operator's Manual of their Model 800 header on page 73. This arrangement provides an additional sealing plate mounted on the cutter bar and extending therefrom rearwardly over the upper surface of the draper, the plate having a downwardly depending edge guide for contacting an upper surface of the draper canvas at a position adjacent the edge of the canvas. This plate had some flexibility relative to the cutter bar so that it could accommodate buildup of materials but the sealing effect was thus reduced. The sealing plate, according to the Manual, was intended for use only with selection of a narrow draper canvas from the choice of the alternative wide and narrow canvases. The use of the narrow canvas provided a cooperation between the edge of the canvas and the rear edge of the cutter bar which was shaped to allow an escape opening between a bottom surface of the cutter bar and the lower run of the draper canvas so that any materials collecting in that area could escape underneath the lower run of the draper canvas to fall to the ground. The draper guide rollers were longer than the width of the canvas so that they projected out from the canvas edges and therefor could become wrapped with the crop material, which of course cannot be tolerated. The support plate for the edge of the canvas was adjusted so that it underlay the edge of the canvas. The canvas edge was thus pinched between the guide edge of the plate and the top surface of the support plate and of the guide rollers.
This arrangement provided a seal which reduced the penetration of the materials into the area between the cutter bar and the draper. However in some cases the crop juices, soil particles and other moisture could cause a buildup of materials in the area between the sealing plate mounted on the cutter bar and the support plate. In some cases these built up materials would be sufficient to trap the edge of the draper canvas to an extent where the edge is damaged. This potential for damage reduced the acceptability of this design which is believed now to have been abandoned.